With experience and innovation, the Maintenance ensures optimum machinery for historical production
With a drawing board in hand, technician Jefferson Gilberto Ferreira Mendes, from the Mechanical Maintenance Division of Generating Units (SMMU.DT), coordinates the last work on the U9 generator. It is necessary to exchange 32 thousand liters of oil of the combined bearing, a time-consuming task that is performed by his colleagues with flying colors. It is mid-December and the team is about to complete the last scheduled maintenance of the year, following 100% the machine stop schedule.
The year’s last maintenance: Jefferson Mendes shows the combined bearing oil level inside the generator.
The daily commitment of the Maintenance team to make the machines available to the company to generate energy is one of the reasons that led Itaipu to surpass the landmark of 100 million MWh of production in 2016. Among the four variables that determine energy production, the availability of generating units is as important as the water flow in reservoir, the transmission system and the consumer market demand. It is also the only factor that is exclusively managed by Itaipu.
According to Cléber Pimenta, being able to stop the machine at the right time optimizes factors like the amount of water and consumption demand.
“With programming, optimization and planning, we have been able to improve machine availability over the years,” explains Cleber Pimenta, Superintendent of Maintenance at Itaipu (SM.DT). Since 2010, the goal is to keep the index above 94% and, for four years, this figure is higher than 96%, i.e., in more than 96% of the time the generating units are available to generate energy.
This increase was made possible thanks to Itaipu Maintenance team’s experience, mainly improved by dismantling and reassembling U6 to enable the turbine wheel repair between September 2010 and March 2012. From this experience in 2012, a review of the company’s Maintenance Plan was planned, and implemented in 2013. Until then, the machine stops occurred on a biannual, annual, biennial and four-yearly basis. As the new plan was implemented, it became biannual, annual, at each 18 months and triennial. The new format reduced the time of stops – the annual one, for example, which consumed nine days happened to be of only one day.
Removal of the turbine wheel from U6. The work conducted between 2011 and 2012 helped in the management of knowledge of the area and guided the Maintenance Plan revision.
“When we changed the maintenance plan, from 2012 to 2013 we took a jump in production. Our time for scheduled maintenance was 4.44% in 2012, and in 2013 we were down to 3.69%,” explains the manager of Maintenance Systemization Division, Marco Aurélo Siqueira Mauro (SMIS.DT). The monitoring of the availability of generating units has been carried out since 1993 and, in the graph it is possible to understand their relation with energy production.
This is because, with the flexibility in the shutdowns of machines throughout the year it was possible to do what the technical area usually calls “dance with the waters”, which means to produce energy according to water availability. As the consumer market (the fourth item among the four factors) is more predictable, the Operation, guided by the National System Operator (ONS) must act according to the amount of water that arrives at the reservoir. And thus the generating units need to be available.
According to Marco Aurélio Mauro, the years of follow-up on the behavior of Gus allow the Maintenance to improve its performance continuously.
“The plan enabled us to optimize stops,” says Mauro. “We opened windows throughout the year that made our schedule more flexible.” That is, when necessary it is possible to move the machine shutdown for months when there is less water and demand for energy.
The schedule of all preventive maintenance is done a year earlier, but a monthly fine adjustment takes place between the Maintenance and Operation teams, which plan and schedule GU shutdowns for the next three months. It is this flexibility of stops that allows achieving such high energy production rates.
In 2016, all scheduled maintenance was carried out, with 13 machines stopped (8 triennial and 5 at each 18 months) or 3.74% of the time of Gus, which is within the average for the last four years. In addition to reflecting the 2012 Plan review, this declining time that units are inoperative shows Itaipu’s newest trait: innovation.
Innovation and Experience
The arrival of new employees in the technical area allowed assigning the element of innovation to Itaipu’s already experienced team of professionals. In Maintenance, multi-year planning coordinates more than 125 priority activities or break away from routine, with proposals for improvements in processes in the areas of safety, training, mechanics, electrical, electronics, laboratory and civil area.
The employees meet every four months for follow-up and, at the end of the year take stock of the activities. All the planning comprises the interval between 2014 and 2023, but a scenario of the next two years is analyzed at each end of the year. “In recent years there has been a lot innovation in the Maintenance processes and this is directly linked to our planning,” says Mauro.
As an example, he cites the oil level monitoring system of a tank that used to be electromechanical and required longer maintenance and was replaced by an electronic-electric system. This innovation alone saved one day from the stop and the work of a whole team, which can focus on another task.
There is a referral to implement process improvement, but it should be performed very carefully. “These improvements reflect machine reliability. The Maintenance area is careful to implement them because you cannot experience the GU. The solution should be ready,” says Pimenta.
Pimenta’s statement refers to a maximum in Maintenance: the number one rule of the area is to maintain the GUs’ reliability, integrity and ensure that they are not defective in the medium or long term. This points to another index, the one of forced unavailability, i.e., when one of these defects happen and it is necessary to perform unscheduled corrective maintenance.
In this historic year 2016, forced maintenance will close by 0.08%, while the business target is to keep it below 0.5%. This years’ index is due, among other causes to a 20-day shutdown, between March and April to correct a leakage of the pure water system, responsible for the cooling of stator bards, at U8. The last time this defect had happened in a similar unit was 22 years ago.
The unexpected event in U8: a leakage of the pure water system from the stator bars required resorting to manuals and experience in order to solve the problem.
“It’s no use increasing machine availability and reducing reliability. It’s a scale that needs to be dosed,” says Mauro. To keep up with the critical work of maintaining the 20 generating units, the area is sustained in a number considered ideal: 18 months.
This is the maximum time of interval that a machine can be without large-size maintenance (at each 18 months or triennial), regardless of consumption demand or amount of water. With planning and an experienced and innovative team, the ideal number – which, due to its importance – is controlled by Itaipu’s Board of Directors – has never been broken in the company.